The life of a spark plug in an internal combustion engine may be affected by the magnitude of electrical current repeatedly passed across a gap in the spark plug to initiate sparks. High electrical currents may cause relatively fast erosion of the plug at the spark plug gap, thereby requiring frequent servicing of the engine to replace the spark plug. Low electrical currents, on the other hand, may not initiate a spark with sufficient intensity to fully and completely ignite a fuel within a combustion chamber of the engine.
Government regulations are increasingly requiring the use of alternative fuels to reduce pollution and emissions. Many of these alternative fuels may only be ignited with a spark having a higher intensity than the spark used to ignite traditional fuels. Accordingly, an engine designed to burn these types of alternative fuels may require an ignition system capable of generating a high intensity spark and, in some cases, an ignition system capable of sustaining a spark for an extended duration.
One example of a system for initiating and sustaining a spark across the gap of a spark plug is disclosed in U.S. Pat. No. 4,345,575 to Jorgensen. The '575 patent discloses an extended duration spark ignition system that has two power sources, a initiation switch, and a sustaining switch. The system includes a series of circuit components on both a primary side and a secondary side of an ignition transformer. The initiation and sustaining switches are on opposite sides of the ignition transformer. Accordingly, the secondary side of the circuit may be more complex than necessary and may include duplicate components, thereby increasing the overall cost of the circuit.
The present invention overcomes one or more of the disadvantages of the prior art.